Police groups have alleged that Chief Whip Andrew Mitchell has doctored a witness statement describing the recent altercation with police at the Downing Street gate where he was alleged to have called them “fucking plebs” and “morons”.

The shock allegation comes after an impartial review of the incident by experienced police officers drafted in from Sheffield.

“We have conducted a full and thorough inquiry into this gross abuse of ministerial power” said West Yorkshire Chief Constable Sir Norman Bettison. “Our conclusion was although the Downing Street gate was badly designed, and the police officers in question may have been asleep, the primary cause of the altercation was Mr Mitchell. I mean what Cabinet Minister cycles when they can take a Ministerial car? Certainly not Eric Pickles.”

Andrew Mitchell has attempted to quell the police fury by apologising for both using bad words and wearing lycra. But the police insist on branding the incident the biggest misuse of power in the last 50 years.

“His original statement tried to blame the plods, I mean policemen, on the gate for provoking him by calling his cycling shorts ‘gay’. He even leaked this information to the Sun newspaper” said outraged Met Police Federation Chairman John Tully. “And then he implied the policemen had lied when he denied using the words ‘fucking plebs’ about the fucking plebs.”

Perhaps the most shocking aspect of the incident is that the Sheffield police allege that the police officers on the Downing Street gate could have been spared hearing bad words if Mr Mitchell had cycled faster and got out the gate before it was closed.